Apple - Disable the use of the "com.apple.quarantine" extended attribute on Mojave

If I understood your question clearly, here is the solution that you can use to disable it completely.

1. Open Terminal

2. Type following command

   sudo defaults write com.apple.LaunchServices LSQuarantine -bool NO
   

3. After that, reboot, and you should be set.

If you want to disable quarantine for files already downloaded

1. Open Terminal.

2. Execute the following command:

   xattr -l /path/to/application/applicationName.app
   

3. You will see output similar to:

   

To remove an extended attribute manually, type the following command in Terminal

   xattr -d com.apple.quarantine /path/to/application/applicationName.app

First run, instead of double-clicking, right click & select Open.

Done.

Alternatively, disable SIP & you get this option back, in Security & Privacy…

… though you still get some 'are you sure?' messages, you can just say 'OK'

After comments: You may also need to set this in Terminal

sudo defaults write /Library/Preferences/com.apple.security GKAutoRearm -bool NO

From Permanently allow apps downloaded from "anywhere"